VGA monitor flickering when HDMI used

[adamthejudge]

This issue has me stumped.

I have a Radeon HD 7800 graphics card with a VGA monitor connected with an adapter into the DVI port and a second VGA monitor with an adapter into the Display Port. This has been working fine.

I then purchased a 10m HDMI cable to hook up my Samsung TV to my computer to make life easier than having to stream. So I connect it all up and when I then power on, the TV display is fine, but my ACER monitor has started flickering.

I tried changing every setting, disabled EDID, changed the refresh rate, changed the resolutions, reinstalled all drivers and ATI software, but nothing seems to stop this annoying flickering.

when I remove the TV output it is fine, and just bought a new monitor (to replace my second one) and that is currently plugged in to HDMI and my acer monitor is fine (no flickering).

Am I missing something or is it just the cable causing the issue? I did notice a small spark when plugging it in (didn't remove the power cable but computer was powered off).

any ideas would be greatly appreciated.

 

[aatu]

Few questions / elaborations:

"Radeon HD 7800":
You mean Radeon HD 7850 or 7870? Or ATI FirePro V7800? What ports does it have? DVI, VGA, Displayport, HDMI?

Monitors/Television:
"VGA monitor"? Do you mean an LCD monitor with a VGA port? Or a CRT monitor with a VGA port? Apparently there's also a Samsung television with an HDMI? And a new monitor, probably an LCD with an HDMI? Which one is the flickering Acer? What ports do they have, each?

DVI-VGA adapter? DisplayPort-VGA adapter?

"Connect it all up"? You mean all three of them?

Disabled EDID? Do you mean override?

Also, is the flicker something like a typical 60Hz CRT flicker, or something like a very annoying 20Hz flicker, or is it some sort of random-interval black pauses?

Which combinations work, and which don't?